1-Imidazolymethyl -substituted -2-naphtols and their use as accelerators for low - temperature curing

ABSTRACT

Compounds of the general formulae (I) and (II): where R 1 , R 2  and R 3  each independently of one another are H;  C1-17 alkyl; C 3-12 cycloalkyl, optionally substituted by C 1-4 alkyl groups; C 4-20 cycloalkyl-alkyl, optionally substituted by C 1-4 alkyl groups; C 6-10 , aryl, optionally substituted by 1-3 C 1-4 alkyl groups, —CN, Hal, OH, or C 1-10 alkoxy; C 7-15 phenylalkyl, optionally substituted by 1-3 C 1-4 alkyl groups; C 3-12 alkenyl; C 3-12 alkynyl; or aromatic or aliphatic C 3-12 acyl; R 4 , R 5 , R 6 , R 7 , R 8 , and R 9  each independently of one another are H; C 1-17 alkyl, C 3-12 Ccycloalkyl, optionally substituted by C 1-4 alkyl groups; C 4-20 cycloalkyl-alkyl, optionally substituted by C 1-4 alkyl groups; C 6-10 aryl, optionally substituted by 1-3 C 1-4 alkyl groups; C 7-15 phenylalkyl, optionally substituted by 1-3 C 1-4 alkyl groups; C 3-17 alkenyl; C 3-12 alkynyl; C 1-12 alkoxy; or OH; for formula (1) R is C 1-12 alkyl; C 3-12 cycloalkyl, optionally substituted by C 1-4 alkyl groups; C 4-20 cycloalkylalkyl; optionally substituted by C 1-4 alkyl groups; C 6-10 aryl, optionally substituted by 1-3 C 1- 4alkyl groups; C 7-15 phenylalkyl, optionally substituted by 1-3 C 1-4 alkyl groups; C 3-12 alkenyl; or C 3-12 alkynyl; and for formula (II) n=2-12; as accelerators in curable epoxy resin compositions which are used as a compression moulding compound, sinter powder, encapsulating system, or casting resin, or for producing prepregs and laminates having very good interlaminar shear strength values using the resin infusion method, wet layup method and injection methods, for producing components, especially components of large surface area.

The invention relates to novel Mannich bases based on1-imidazolylmethyl-substituted 2-naphthol compounds and also to theiruse as accelerators for epoxy resin systems which allow high ILS valuesin laminates, particularly for impregnation by resin infusion methods,the wet layup method and other impregnating methods. The accelerators ofthe invention are additionally suitable for sinter powder, casting resinand compression moulding compound applications.

The compound 1-imidazolylmethyl-2-naphthol and other imidazole catalystsand accelerators in connection with epoxy resins are known.

The customarily used imidazoles such as imidazole, 1-methylimidazole,2-methylimidazole, 2-ethyl-4-methylimidazole or else 2-phenylimidazoles,however, in many epoxy resin formulations produce inadequate storagestabilities of prepregs at room temperature when they are employed inprepreg formulations.

In the past attempts have been made to solve this problem by looking toreduce the reactivity of the imidazoles by formation of salts withorganic or inorganic acids: see U.S. Pat. No. 3,356,645 and U.S. Pat.No. 5,001,212, for example. Although improvements in the storagestabilities of prepregs (standing times for short) were achieved inthose cases, they are still not sufficient for many applications.

Another way of improving the standing times of prepregs is to formimidazole complexes by reacting imidazoles with metal salts: see U.S.Pat. No. 4,101,514 and U.S. Pat. No. 4,487,914, for example. Generallyspeaking, the improvement in the standing times that can be achieved inthis way is obtained at the expense of an increase in the processingtemperatures. Moreover, the metal complexes present in the cured epoxyresin system lead to a deterioration in the dielectric values and alsoto an increase in the water absorption. In many applications, however,it is required that there is no substantial change in water absorption,since otherwise the glass transition temperature may be lowered, whichcan lead to a considerable change in the mechanical, electrical andthermal properties of the impregnated component.

EP 0 761 709 describes 1-imidazolylmethyl-substituted 2-naphtholcompounds as catalysts which make it possible substantially to avoid thedisadvantages described in the above citations. The compounds inquestion are stable Mannich bases which in epoxy resin systems lead to amarkedly improved standing time of the overall system at roomtemperature. A formulation comprising such a catalyst can be curedrapidly in the temperature range between 110° C. and 150° C. Materialsof this kind exhibit good mechanical properties with relatively highglass transition ranges. Prepregs comprising such catalysts can bestored without problems for up to 16 days at room temperature andprocessed to laminates.

Established methods for producing favourably priced components of largesurface area include resin infusion methods and other impregnatingmethods. In order to be able to be used in resin infusion methods, suchas RTM, the epoxy resin formulation for use ought to have a viscosity ofbetween 100 and 1000 mPa·s, but preferably from 100 mPa·s to 500 mPa·s,at a temperature of from 23° C. to 60° C. For reasons of cost, the aimis for temperatures below 100° C. during the impregnating operation.When, for example, the wet layup method is chosen for components oflarge surface area, the curing temperatures ought to remain well below100° C., again on economic grounds. For reasons of greater ease ofhandling the semi-finished products manufactured in this way (prepregs)ought to have a relatively long storage stability at room temperature,which means that the prepreg must be capable of troublefree conversionto the laminate after storage for, for example, four days or more. Wherelaminates produced in this way are employed in energy-producinginstallations, the laminates being subject to rotational movements andconsiderable shear forces during their use, a certain minimum ofadhesion is necessary between the individual layers which make up thelaminate. One measure of this adhesion is that known as interlaminarshear strength, also called ILS for short, which is determined inaccordance with the ASTM standard (ASTM D 2344-84). A maximum ILS valueis therefore an aim for such applications.

It has now been found that 1-(imidazolyl-2-methyl)-2-naphthol doesenable outstanding storage stabilities at room temperature in prepregformulations but not very high interlaminar shear strength values. Themaximum achievable value is approximately 22 MPa, irrespective ofwhether curing is carried out at 60° C. for four hours, at 75° C. forfour hours or even eight hours or at 140° C. for 30 minutes.

It has now surprisingly been found that Mannich bases based on1-imidazolylmethyl-substituted 2-naphthol compounds, whose free aromatichydroxyl group is alkylated, have a profile of properties which allowstheir advantageous use as accelerators for epoxy resin systemsparticularly for the resin infusion method, the wet layup method andimpregnating methods, since semi-finished articles impregnated in thisway, in addition to a prepreg storage stability of 2-8 days, also giveILS values of up to 50 MPa when cured at 60° C. or 75° C. for from fourto eight hours.

The present invention accordingly first provides compounds of thegeneral formulae (I) and (II):

whereR₁, R₂ and R₃ each independently of one another are H; C₁₋₁₇alkyl;C₃₋₁₂cycloalkyl, optionally substituted by C₁₋₄alkyl groups;C₄₋₂₀cycloalkyl-alkyl, optionally substituted by C₁₋₄alkyl groups;C₆₋₁₀aryl, optionally substituted by 1-3 C₁₋₄alkyl groups, —CN, Hal, OH,or C₁₋₁₀alkoxy;C₁₋₁₅phenylalkyl, optionally substituted by 1-3 C₁₋₄alkyl groups;C₃₋₁₂alkenyl; C₃₋₁₂alkynyl; oraromatic or aliphatic C₃₋₁₇acyl;R₄, R₅, R₆, R₇, R₈ and R₉ each independently of one another are H;C₁₋₁₇alkyl; C₃₋₁₂Cycloalkyl, optionally substituted by C₁₋₄alkyl groups;C₄₋₂₀cycloalkyl-alkyl, optionally substituted by C₁₋₄alkyl groups;C₆₋₁₀aryl, optionally substituted by 1-3 C₁₋₄alkyl groups;C₇₋₁₅phenylalkyl, optionally substituted by 1-3 C₁₋₄alkyl groups;C₃₋₁₇alkenyl; C₃₋₁₂alkynyl; C₁₋₁₂alkoxy; or OH; for formula (I)R is C₁₋₁₂alkyl; C₃₋₁₂cycloalkyl, optionally substituted by C₁₋₄alkylgroups;C₄₋₂₀cycloalkyl-alkyl, optionally substituted by C₁₋₄alkyl groups;C₆₋₁₀aryl, optionally substituted by 1-3 C₁₋₄alkyl groups;C₇₋₁₅phenylalkyl, optionally substituted by 1-3 C₁₋₄alkyl groups;C₃₋₁₂alkenyl; or C₃₋₁₂alkynyl; and for formula (II) n=2-12.

Preferred compounds of the general formulae (I) and (II) in respect ofthe radicals R₁, R₂ and R₃ are those where R₁, R₂ and R₃ are eachindependently of one another H;

C₁₋₁₂alkyl; phenyl; or C₇₋₁₅phenylalkyl, optionally substituted by 1-3C₁₋₄alkyl groups; particular preference is given to compounds where R₂and R₃ are each H; and R₁ is C₁₋₁₂alkyl; phenyl; or C₇₋₁₅phenylalkyl,optionally substituted by 1-3 C₁₋₄alkyl groups.

Preferred compounds of the general formula (I) in respect of the radicalR are those where R is C₁₋₁₂alkyl; or C₃₋₁₂alkenyl; and preferredcompounds of the general formula (II) are those where the factor n=6-12in respect of the unsubstituted aliphatic —CH₂)—(CH₂)_(n)—CH₂— bridge.

Preferred compounds of the general formulae (I) and (II) in respect ofthe radicals R₄ to R₉ are those for which the stated radicals are ahydrogen atom (H).

The stated preferences for compounds of the general formulae (I) and(II) in respect of the radicals R₁, R₂ and R₃; of the radicals R₄ to R₉;of the radical R for compounds of the general formula (I), and inrespect of the factor n for compounds of the general formula (II) alsoapply in any desired combination.

Particular preference is given to compounds of the general formulae (I)and (II) in which the radicals R₂ to R₉ are a hydrogen atom, and theradical R₁ is C₁₋₄alkyl (methyl, ethyl, n,i-propyl, n,i,t-butyl), orphenyl, optionally substituted by 1-3 C₁₋₄alkyl groups, and R isC₃₋₁₂alkyl or C₃₋₁₂alkenyl, and for formula (II) n=8, 10, or 12.

Special preference is given to compounds where R₁=methyl, R₂₋₉ are eacha hydrogen atom, R=n-butyl, n-nonyl, n-dodecyl, or allyl, and n=8.

The compounds of the invention can be prepared by methods which areknown per se. For this purpose, first of all a1-imidazolylmethyl-substituted 2-naphthol is prepared as described, forexample, in EP 0 761 709 A. The hydroxyl group of the naphthol issubsequently etherified by conventional means, preferably in an alkalimedium. In the case of the compounds of the formula (II) ring systemswhich are identical in each case are bridged by an aliphatic,unsubstituted hydrocarbon chain.

As mentioned at the outset, the compounds of the invention are suitableas accelerators for curable epoxy resin systems.

The invention therefore further provides curable epoxy resincompositions comprising

a) an epoxy resin whose epoxide content is from 0.1 to 11, preferablyfrom 0.1 to 2.2, epoxide equivalents/kg,

b) a compound of the formula (I) or (II),

c) a curing agent for the epoxy resin, and optionally

d) an additive customary in epoxy resin technology.

In principle all epoxy resins are suitable as component (a).

Suitable examples include diglycidyl or polyglycidyl ethers ofcycloaliphatic polyols, such as 2,2-bis(4′-hydroxycyclohexyl)propane,diglycidyl or polyglycidyl ethers of polyhydric phenols, such asresorcinol, bis(4′-hydroxyphenyl)methane (bisphenol F),2,2-bis(4′-hydroxyphenyl) propane (bisphenol A),2,2-bis(4′-hydroxy-3′,5-dibromophenyl)propane,1,1,2,2-tetrakis(4′-hydroxyphenyl)ethane, or condensation products ofphenols with formaldehyde, such as phenol novolaks and cresol novolaks;additionally, di- or poly(β-methylglycidyl) ethers of the above-citedpolyalcohols and polyphenols; polyglycidyl esters andpoly(β-methylglycidyl)esters of polybasic carboxylic acids such asphthalic acid, terephthalic acid, tetrahydrophthalic andhexahydrophthalic acid; glycidyl derivatives of aminophenols, such astriglycidyl-p-aminophenol; N-glycidyl derivatives of amines, amides andheterocyclic nitrogen bases, such as N,N-diglycidylaniline,N,N-diglycidyltoluidine,N,N,N′,N′-tetraglycidyl-bis(4-aminophenyl)methane, triglycidylisocyanurate, N,N-diglycidyl-N,N′-ethyleneurea,N,N′-diglycidyl-5,5-dimethylhydantoin,N,N′-diglycidyl-5-isopropylhydantoin,N,N′-diglycidyl-5,5-dimethyl-6-isopropyl-5,6-dihydrouracil;polyfunctional epoxy resins, such as the 2,6-disubstituted4-epoxypropylphenyl glycidyl ethers and adducts thereof that aredescribed in EP-A 205 409 and EP-A 204659; bisphenols such substitutedwith in each case two glycidyloxy groups and 2,3-epoxypropyl groups,such as the 2,2-bis(3′-epoxypropyl-4′-epoxypropylphenyl)propanedescribed in GB 828364; glycidyl derivatives oftetramethylol-substituted cyclohexanols, cyclohexanones, cyclopentanolsand cyclopentanones, such as the compounds described in U.S. Pat. No.4,549,008; glycidyloxy-substituted benzophenones; andglycidyloxydiketones, such as the compounds described in U.S. Pat. No.4,649,181.

In general it is also possible to use mixtures of two or more epoxyresins as components in the formulations of the invention.

Suitable epoxy resins include preferably glycidyl ethers such asbisphenol A or F, glycidyl esters, N-glycidyl and N,O-glycidylderivatives of aromatic or heterocyclic compounds, and alsocycloaliphatic glycidyl compounds. They preferably have a functionalityof from 0.1 to 2.2 epoxide equivalents/kg.

As curing agents, or component (c), it is possible in principle to useall of the curing agents which are customary in epoxy resin chemistry,such as amines, dicyandiamide, cyanoguanidines, melamines, novolaks,including cresol-novolaks, polyols and anhydrides, for example.

Curing agents suitable in principle also include the dihydroxy aromaticssuch as the bisphenols or diphenols already mentioned. Besides diphenolsR is also possible to use triphenols or polyphenols, such as2,4,6-tris[2′-(p-hydroxyphenyl)-2′-propyl]benzene (from MitsuiPetrochemical), for example.

As curing agent it is preferred to use amines and polyamines, examplesbeing those of the Jeffamine D and T type, and others. Examples that maybe mentioned include o-, m-, and p-phenylenediamine; diaminotoluenes,such as 2,4-diaminotoluene, 1,4-diamino-2-methoxy-benzene,2,5-diaminoxylene, 1,3-diamino-4-chlorobenzene,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether,4,4′-diaminodiphenyl thioether, 4,4′-diaminodiphenyl sulfone,2,2′-diaminobenzophenone, 1,8- or 1,5-diaminonaphthalene,2,6-diaminopyridine, 1,4-piperazine, 2,4-diaminopyrimidine,2,4-diamino-s-triazine, di-, tri-, tetra, hexa-, hepta-, octa-, anddecamethylenediamine, 3-methylheptamethylene-1,6-diamine,3-methoxyhexamethylenediamine, 2,11-diaminododecane, 2,2,4- and2,4,4-trimethylhexamethylenediamine, 1,2-bis(3-aminopropoxy)ethane,N,N′-dimethylethylenediamine, N,N′-dimethyl-1,6-diamino-hexane and alsothe diamines of the formulae

H₂N(CH₂)₃O(CH₂)O(CH₂)₃NH₂ and H₂N(CH₂)₃S(CH₂)₃NH₂,1,4-diaminocyclohexane, 1,4-bis(2-methyl-4-aminopentyl)benzene,1,4-bis(aminomethyl)benzene.

Additionally suitable amines are carbocyclic-aromatic diamines,especially substituted dinuclear diamines, such asbis(3,5-diisopropyl-4-aminophenyl)methane,bis(2-chloro-3,5-di-ethyl-aminophenyl)methane,bis(3-ethyl-4-amino-5-sec-butylphenyl)methane,bis(2-chloro-3,5-diethyl-4-aminophenyl)methane andbis(3,5-diethyl-4-aminophenyl)methane, for example.

Additionally suitable are propane-1,3-diamine, m-xylenediamine,bis(4-aminocyclohexyl)-propane,3-aminomethyl-3,5,5-trimethylcyclohexylamine(isophoronediamine),polyaminoamides, examples being those consisting of aliphatic polyaminesand dimerized or trimerized fatty adds; polyphenols, such as resorcinol,hydroquinone, bisphenol A and phenol/aldehyde resins, and alsopolythiols such as “Thiokols” for example.

Preferred curing agents are diamines or polyamines, amino-terminatedpolyalkylene glycols (e.g. Jeffamines, amino-poly-THF) orpolyaminoamides, especially dimers or copolymers of propylene glycol andethylene glycol, amino-terminated polybutadienes with molecular weightsin the range from about 150 to 5000, in particular from 200 to 600.

Particularly preferred curing agents am amino-terminatedpolyetherdiamines, especially short-chain polyoxyalkylenediamines with asmall (less than 10, preferably less than 6) repetition factor inrespect of the polyoxyalkylene units. As commercially available curingagents mention may be made of Jeffamine® D230, a polyoxypropylenediaminecontaining on average 2.6 oxypropylene units.

As optional component d) it is possible to use additives customary inepoxy resin technology. By these are meant the customary auxiliaries andadditives which are known to and used by the person skilled in the artin respect of the particular application. Examples include organic andinorganic fillers and pigments, release agents, andviscosity-influencing additives.

To prepare the curable compositions of the invention the accelerators ofthe invention are dissolved beforehand in the curing agent, at generallyelevated temperatures: for example, when using a Jeffamine®, at about80° C. Solutions of this kind can be cooled to 40° C. and then mixedwith the epoxy resin. These mixtures can then be used directly as an RTMor impregnating solution. Another possibility is to disperse theaccelerators of the invention homogeneously in the epoxy resinbeforehand, by means for example of suitable stirrers, such as anUltra-Turrax or a triple roll mill.

The compounds of the invention are used advantageously at from 1 to 10parts by weight, based on the overall formulation. It is particularlyadvantageous to use from 5 to 7 parts by weight. The curing agents areemployed in the customary amounts, which are therefore to be calculatedsuch that on average per epoxide group there are from 0.5 to 1.5,preferably from 0.8 to 1.2, functional groups of the curing agent.Auxiliaries and additives can be used in principle in wide quantityranges, provided that this is possible without a significant increase inthe viscosity of the desired compositions.

As already mentioned, the compounds of the invention lower the storagestabilities of prepregs when they are used, for example, in epoxyresin/amine formulations and the prepregs thus prepared are stored atroom temperature. However, prepregs comprising inventive accelerators ofthis kind have the capacity to give an ILS value of up 50 MPa.Accordingly the accelerators of the invention are particularly suitablefor use in epoxy resin formulations which are employed as compressionmoulding compounds, sinter powders, encapsulating systems, castingresins and for producing prepregs and laminates by the resin infusionmethod, wet layup method and injection methods.

EXPERIMENTAL SECTION

a) Preparation of the Mannich Bases. General Description of theEtherification of a Naphthol, Using 1-imidazotlymethyl-2-naphthol asExample. Alkaline Variant in DMSO

A sulphonating flask (300-400 ml) provided with reflux condenser,internal thermometer, dropping funnel and KPG stirrer is charged withdimethyl sulphoxide and then the chosen naphthol is added with stirring.This gives a beige suspension. KOH in powdered form is added to thestirred solution. The solution changes its colour from beige to greenand clarifies over the course of about 15 minutes to form a deep-greensolution which still contains a few solid fractions. The internaltemperature within the flask is approximately 22° C. At this temperaturethe alkyl halogen or the alkyl dihalogen, respectively, is addeddropwise. The mixture is warmed to 30° C. over 15 minutes. Then theremaining haloalkyl or dihaloallyl is added over a further nine minutes.The contents of the flask are heated initially to just over 50° C. andthen to about 70° C. The flask is stirred at this temperature fortwo-three hours. Thereafter the reaction solution is poured onto 150 gof ice. A beige-brown solid and a milky aqueous phase are obtained. Theorganic phase is separated from the aqueous phase and the latter isextracted by shaking five times with 50 ml of toluene each time. Thecombined organic phases are dried over anhydrous sodium sulphate. Afterovernight standing and the removal of the drying agent on a suctionfilter, the solvent is removed on a rotary evaporator. This crudeproduct is taken up in 20 ml of isopropanol and heated under reflux toabout 65° C. The product is frozen out of the solution using dry ice,and isopropanol is removed on a suction filter. Finally the solid isdried at about 40° C./0.3 mbar for about two hours. The amounts of theindividual components used can be found in Table 1 below. TABLE 1 E¹⁾Comp. 1²⁾ Comp. 2²⁾ Comp. 3²⁾ Solv.³⁾ Yld.⁴⁾ M.p⁵⁾ 1 11.91 (50)  10.56(51)  3.08 (55)  100 80-86 83 2 35.73 (150) 18.91 (153) 9.24 (165) 30037 93 3 35.73 (150) 38.13 (153) 9.24 (165) 300 91 81 4 35.73 (150) 14.16(153) 9.24 (165) 300 85 91 5 28.59 (120) 18.0 (60) 7.08 (126) 300 48 158¹⁾E = experiment;²⁾Comp. = component, amount in g and mmol ( ), component 1 =1-imidazolylmethyl-2-naphthol, component 2 for E1 = nonyl bromide, E2 =allyl bromide, E3 = dodecyl bromide, E4 = butyl chloride, E5 =1,10-dibromododecane; component 3 = KOH³⁾Solv. = solvent in ml, solvent in above experiments is in each casedimethyl sulphoxide (DMSO);⁴⁾Yld. = yield in %;⁵⁾m.p = melting point (DSC) in ° C. Further characterization of theproducts was by ¹H and ¹³C NMR (d₆-DMSO) and C, H, N, O analyses.

The compounds of the invention are advantageously added in from 1 to 10parts, in particular from 5 to 7 parts, by weight to the desiredformulation. See also Table 2 in this regard.

b) Use Examples of the Mannich Bases of the Invention

The products from the above experimental section a) are dissolved attemperatures between 60° C. and 80° C. in the amine curing agent. Thisgives orange to dark brown clear solutions. After cooling to roomtemperature, this solution is admixed with the calculated amount ofepoxy resin. For details see Table 2 below: TABLE 2 ExperimentComparison E6 E7 E8 E9 E10 LY 556¹⁾ 100 100 100 100 100 100 Jeffamine²⁾10 10 10 10 10 8 Accelerator³⁾ 10 E1⁴⁾ 7 E2⁴⁾ 5 E3⁴⁾ 5 5 3 DY 965⁵⁾ 5 10Minimum viscosity at 800-1000 150 150 150 Ng¹¹⁾ 150 60° C. [mPa · s]¹²⁾Preparation⁶⁾ 8 2-7 2 2 2 2 Prepreg⁷⁾ 12 12 ? 12 12 12 Resin content⁸⁾40-42 40-42 40-42 40-42 40-42 40-42 Storage⁹⁾ RT RT RT RT RT RTInterlaminar shear strength (ILS) after 30 min at 140° C.: F_(max)[N]¹⁰⁾ 601 +/− 38 2067 +/− 52  2109 +/− 52  1201 +/− 33  989 +/− 62 1037+/− 20  σ_(max) [MPa]¹⁰⁾ 22.6 +/− 1.4 50.9 +/− 1.2  52 +/− 0.7 44.2 +/−1.5 38.2 +/− 2.5 34.6 +/− 0.7 Interlaminar shear strength (ILS) after 4h at 75° C.: F_(max) [N] 426 +/− 37 496 +/− 30 Ng 964 +/− 73 1074 +/−35  1082 +/− 29  σ_(max) [MPa] 16.0 +/− 1.4 13.4 +/− 0.7 Ng 38.1 +/− 1.840.3 +/− 0.9 40.6 +/− 1.3 Interlaminar shear strength (ILS) after 8 h at75° C.: F_(max) [N] 400 +/− 33 1271 +/− 125 Ng 959 +/− 48 927 +/− 361182 +/− 102 σ_(max) [MPa] 16.0 +/− 1.3 43.0 +/− 4.0 Ng 38.6 +/− 1.737.7 +/− 1.3 45.4 +/− 3.3 Interlaminar shear strength (ILS) after 4 h at60° C.: F_(max) [N] Nm¹¹⁾ 2132 +/− 14  Ng Ng Ng Ng σ_(max) [MPa] Nm¹¹⁾ 50 +/− 0.4 Ng Ng Ng Ng¹⁾Araldite LY 556 Bisphenol-A Harz (Vantico AG)²⁾Jeffamine Jeffamine D-230 (Huntsman)³⁾XU 3123 1-Imidazolylmethyl-2-naphthol (Vantico AG)⁴⁾E1/E2/E3 Experiments 1, 2 and 3 (see Table 1)⁵⁾DY 965 Flexibilizing agent DY 965 (Vantico AG)⁶⁾Preparation Preparation of the prepregs and laminates after number ofdays⁷⁾Prepreg Number of plies = 12⁸⁾Resin content1 Resin content in per cent after compression of thelaminates⁹⁾Storage At 20° C. to 25° C. = RT¹⁰⁾F_(max) Ultimate strength (breaking load) to ASTM D 2344σ_(max) Shear strength to ASTM D 2344¹¹⁾Nm, Ng Nm = not measurable, Ng = not measured¹²⁾Viscosity Determined using Rheometrix RD2 with a plate/plate setup

Surprising are the very good interlaminar shear strengths which can beobtained with the accelerators of the invention in the lower temperaturerange (60° C. and 75° C./48 hours), see Table 2, Formulations E6, E7 andComparison. The values found are substantially higher than in the caseof the comparison system. The viscosity level of 150 mPa·s which can beachieved with the accelerators of the invention at 60° C. is also wellbelow that of the comparison system, of 800-1000 mPa·s at 60° C. This isa key further advantage of the accelerators of the invention with a viewto their use in infusion methods, since low viscosities are requiredtherein.

1-12. (canceled)
 13. A compound of general formula (I) or (II):

where R₁, R₂, and R₃ each independently of one another are H; C₁₋₁₇alkyl; C₃₋₁₂ cycloalkyl, optionally substituted by C₁₋₄ alkyl groups;C₄₋₂₀ cycloalkyl-alkyl, optionally substituted by C₁₋₄ alkyl groups;C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkyl groups, —CN, HaI,OH, or C₁₋₁₀ alkoxy; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3C₁₋₄ alkyl groups; C₃₋₁₂ alkenyl; C₃₋₁₂ alkynyl; or aromatic oraliphatic C₃₋₁₂ acyl; R₄, R₅, R₆, R₇, R₈ and R₉ each independently ofone another are H; C₁₋₁₇ alkyl; C₃₋₁₂ cycloalkyl, optionally substitutedby C₁₋₄ alkyl groups; C₄₋₂₀ cycloalkyl-alkyl, optionally substituted byC₁₋₄ alkyl groups; C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₃₋₁₇ alkenyl; C₃₋₁₂ alkynyl; C₁₋₁₂ alkoxy or OH; for formula(I) R is C₁₋₁₂ alkyl; C₃₋₁₂ cycloalkyl, optionally substituted by C₁₋₄alkyl groups; C₄₋₂₀ cycloalkyl-alkyl, optionally substituted by C₁₋₄alkyl groups; C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₃₋₁₂ alkenyl; or C₃₋₁₂ alkynyl; and for formula (II) n=2-12.14. A compound according to claim 13, where R₁, R₂ and R₃ eachindependently of one another are H; C₁₋₁₇ alkyl; phenyl; or C₇₋₁₅phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkyl groups.
 15. Acompound according to claim 14, where R₂ and R₃ each H; and R₁ is C₁₋₁₇alkyl; phenyl; or C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄alkyl groups.
 16. A compound according to claim 13, where for formula(I) R is C₁₋₁₂ alkyl or C₃₋₁₂ alkenyl; and for formula (II) n=6-12. 17.A compound according to claim 13, where R₄, R₅, R₆, R₇, R₈ and R₉ are H.18. A compound according to claim 13, where R₁ is methyl; R₂, R₃, R₄,R₅, R₆, R₇, R₈ and R₉ are H; R is n-butyl, n-nonyl, n-dodecyl, or allyl;and n=8.
 19. A curable composition comprising: a) an epoxy resin whoseepoxide content is from 0.1 to 11 epoxide equivalents/kg; b) from 1 to10 parts by weight, based on the total weight of the curablecomposition, of a compound of formula (I) or (II):

where R₁, R₂, and R₃ each independently of one another are H; C₁₋₁₇alkyl; C₃₋₁₂ cycloalkyl, optionally substituted by C₁₋₄ alkyl groups;C₄₋₂₀ cycloalkyl-alkyl, optionally substituted by C₁₋₄ alkyl groups;C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkyl groups, —CN, HaI,OH, or C₁₋₁₀ alkoxy; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3C₁₋₄ alkyl groups; C₃₋₁₂ alkenyl; C₃₋₁₂ alkynyl; or aromatic oraliphatic C₃₋₁₂ acyl; R₄, R₅, R₆, R₇, R₈ and R₉ each independently ofone another are H; C₁₋₁₇ alkyl; C₃₋₁₂ cycloalkyl, optionally substitutedby C₁₋₄ alkyl groups; C₄₋₂₀ cycloalkyl-alkyl, optionally substituted byC₁₋₄ alkyl groups; C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₃₋₁₇ alkenyl; C₃₋₁₂ alkynyl; C₁₋₁₂ alkoxy or OH; for formula(I) R is C₁₋₁₂ alkyl; C₃₋₁₂ cycloalkyl, optionally substituted by C₁₋₄alkyl groups; C₄₋₂₀ cycloalkyl-alkyl, optionally substituted by C₁₋₄alkyl groups; C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₃₋₁₂ alkenyl or C₃₋₁₂ alkynyl; and for formula (II) n=2-12; c)a curing agent for the epoxy resin having from 0.5 to 1.5 functionalgroups per epoxide group; and optionally d) one or more additives.
 20. Acurable composition according to claim 19, wherein the curing agent isan amine or polyamine.
 21. A curable composition according to claim 20,wherein the curing agent is a polyoxypropylenediamine.
 22. A curablecomposition according to claim 19, wherein the epoxy resin is a glycidylether, glycidyl ester, N-glycidyl or N,O-glycidyl derivative of anaromatic or heterocyclic compound, or a cycloaliphatic glycidylcompound.
 23. A method for making a curable composition comprisingadding to an epoxy resin a curing agent and a compound of formula (I) or(II):

where R₁, R₂, and R₃ each independently of one another are H; C₁₋₁₇alkyl; C₃₋₁₂ cycloalkyl, optionally substituted by C₁₋₄ alkyl groups;C₄₋₂₀ cycloalkyl-alkyl, optionally substituted by C₁₋₄ alkyl groups;C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkyl groups, —CN, HaI,OH, or C₁₋₁₀ alkoxy; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3C₁₋₄ alkyl groups; C₃₋₁₂ alkenyl; C₃₋₁₂ alkynyl; or aromatic oraliphatic C₃₋₁₂ acyl; R₄, R₅, R₆, R₇, R₈ and R₉ each independently ofone another are H; C₁₋₇ alkyl; C₃₋₁₂ cycloalkyl, optionally substitutedby C₁₋₄ alkyl groups; C₄₋₂₀ cycloalkyl-alkyl, optionally substituted byC₁₋₄ alkyl groups; C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₃₋₁₇ alkenyl; C₃₋₁₂ alkynyl; C₁₋₁₂ alkoxy or OH; for formula(I) R is C₁₋₁₂ alkyl; C₃₋₁₂ cycloalkyl, optionally substituted by C₁₋₄alkyl groups; C₄₋₂₀ cycloalkyl-alkyl, optionally substituted by C₁₋₄alkyl groups; C₆₋₁₀ aryl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₇₋₁₅ phenylalkyl, optionally substituted by 1-3 C₁₋₄ alkylgroups; C₃₋₁₂ alkenyl or C₃₋₁₂ alkynyl; and for formula (II) n=2-12. 24.The method of claim 23 wherein the compound of formula (I) or (II) isdissolved beforehand in the curing agent at a temperature between60°-80° C.
 25. A prepreg comprising a curable composition according toclaim 19.